Recovery process and apparatus



Oct. 28, 1969 K. R. BOWMAN RECOVERY PROCESS AND APARATUS 2 Sheets-Sheet 1 Filed July 1, 1966 K. R. BOWMAN RECOVERY PROCESS AND APPARATUS Oct. 28, 1969 2 Sheets-Sheet 2 Filed July l. 1966 United States Patent O U.S. Cl. 201-32 13 Claims ABSTRACT F THE DISCLOSURE There is disclosed herein a process and apparatus for enabling constituents to be separated from material such as coal, shale, and so forth. A substantially airtight enclosure is provided, and included therein is a moving perforated belt upon which is disposed a several inch layer of the material. The top of the material layer is heated by a radiant energy source in a manner to provide a hot upper layer of material and a substantially cooler lower layer of material through which vaporized constituents may condense to a liquid form. Released liquid constituents ow to a drain, and gas retrieving ducts are provided for withdrawing released gases by means of a cyclonic separator. A` pressure regulator is coupled between the output of the separator back to the enclosure above the bed to maintain the pressure within the heating chamber near atmospheric pressure and the bed is maintained slightly below atmospheric pressure. The closed system prevents the oxidation of the material or products thereof, and prevents the expulsion of gas from tiny holes in the enclosure. The return of gas to the enclosure below the heating source provides a gas shield to prevent released gases from the bed from being burned by, or caked on, the heating source.

This invention relates to a recovery process and apparatus and more particularly to a process and apparatus for heat treating material, such as coal, to recover therefrom constituents or products, such as natural gases, oils and coke.

Various processes and apparatus have been devised for separating constituents, such as volatile matter, from materials such as coal, shale, etc. Storrs Patent No. 2,890,- 154, for example, discloses the heat treatment of coal in which coal is passed through an open longitudinal heating area wherein the coal is heated causing the release and separation of various products as the coal passes along the heating area. According to the patent, the coal is heated only to the point at which the constituents, other than natural gas, are driven off in liquid form. It is not understood how the constituents can be driven olf in liquid form, and inasmuch as the coal is tumbled by vibrators to ensure uniform heating, apparently condensation does not take place. Furthermore, the use of an open system allows the highly volatile gases to exist in the vicinity of the apparatus creating an explosion hazard.

Trent Patent No. 1,814,463 describes a system for carbonizing coal wherein a longitudinal retort is employed through which a bed of coal is passed, the coal being heated from above and `condensed volatiles being recovered below. Trent employs a very thin bed of coal deposited on a conveyor, and successive independent heating zones maintained at dilerent temperatures. His products of distillation condense in an elongated pan or several pans. Tripp et al. Patent No. 2,658,061 is directed to an apparatus for separating oil from oil shale. The shale is fed to and conveyed along an upwardly extending conveyer and the shale is heated by gas. The gas used for heating picks up the rising vapors from the shale and carries them through cool shale above the entrance of Patented Oct. 28, 1969 "lee the conveyer to condense the vapors and preheat the cool shale.

Prior processes and apparatus of the nature of those discussed above have not provided entirely satisfactory results. In particular, the use of a thin bed of material, vibration thereof, or preheating the incoming material prevents the efcient condensation of the released constituents. Furthermore, these prior processes and apparatus cannot readily be modied so as to process larger amounts of material in a simple and eicient manner.

Accordingly, it is an object of the present invention to enable constituents to be separated from materials such as coal, shale, etc., in an improved manner.

It is an additional object of this invention to provide an improved process and apparatus for separating products from coal, shale, and the like by providing an improved manner in which said material is heated and the products are condensed.

It is a further object of this invention to provide a continuous process for separating constituents from material particles in which relatively cool particles in a lower portion of a bed of said material particles substantially along the entire length thereof condense vapors released by relatively hot particles in an upper portion of said beds.

Another object of the invention is to provide an apparatus in which a suiciently thick bed of material particles is conveyed under a heat source to cause upper particles to be heated and constituents therein to be vaporized while allowing the constituents to condense through relatively cooler lower particles substantially along the length of the entire bed.

These and other objects of this invention will become more apparent upon a consideration of the following description taken in conjunction with the drawings in which:

FIGURE l is an illustration of the process and apparatus of the present invention;

FIGURE 2 is a diagram of the manner in which products are released from a bed of material and condensed according to the invention;

FIGURE 3 is a cross-sectional partial perspective view of apparatus according to the present invention;

FIGURE 4 is a side elevational view of the apparatus illustrated in FIGURE 3; and

FIGURE 5 is a cross-sectional view of a portion of the apparatus shown in FIGURE 3.

In accordance with the present invention, material partlcles `from which constituents may be extracted are formed into an elongated bed Iwithin an enclosure and heated substantially along the entire length of the bed. The bed is moved continuously as it is being heated whereby the bed essentially includes a heated upper layer of particles with relatively cooler particles beneath. Heating of the particles progresses downward through the bed and causes the release or vaporization of various products or constituents from the material, vaporized liquids being condensed by passing the cool lower particles substantially along the entire length of the bed. Means are provided for withdrawing the condensed products and released gases, as well as the remaining material particles from which the products have been released. A closed system is provided to prevent the oxidation of the material or products, and the withdrawn gas may be returned above the bed to maintain an appropriate pressure within the enclosure.

The present invention enables the processing of various materials, such as coal, oil shale, bituminous sands, carbonaceous fossil, tar sand, and so forth to remove products such as oil and gas therefrom. After removing these products from materials such as coal, the resulting coke may be withdrawn for subsequent use for heating purposes. The resulting liquids, such as oil, may be used for various purposes well known in the art, but typically after further rening thereof. Resulting gases may be captured for subsequent use, and some gas may be retui-ned above the bed as mentioned previously. Similarly, the gases may be used in heating the bed of material.

Turning now to the drawings, material to be processed is stored in a bin and fed through an elevator 11 and a conventional feeder 12, which functions as an air-lock, to a horizontal retort. The material forms a bed '13 ori a perforated belt 14. Although not intending. to be limited thereby, the present invention will be described in terms of processing coal, it being appreciated that various other materials from which volatile matter may be extracted can be used.

The perforated belt 14 is moved by drums 15 and 16 within an essentially air-tight enclosure 17, and the belt 14 moves the bed 13 of material past heating elements or rods 18. The bed of material 13 after being processed exits from the end of the belt 14 and is withdrawn by means of an elevator 19. As will appear subsequently, constituents released from the bed of material 13 upon heating are condensed'through a cool lower layer of the material. The resulting liquid passes through the perforated belt 14 and through take-off tubes 20 and 21 to a storage tank 22.

The bed of material after being processed, hereinafter referred to as char or coke, is carried by the elevator 19 though an air-lock feeder 24 to a vertical calciner 25. Steam may be injected up through the withdrawn char or coke in the vertical calciner 25 to strip the remainder of the volatile matter therefrom, which in turn may be separated from dust particles, and the like, cleaned and returned to the tank 22. Another elevator 26 carries the coke into a storage tank 27.

Turning now to FIGURE 2, a portion of thebelt 14 is shown moving a bed 13 of coal under the heating rods 18 having insulation 30 arranged thereaboye. As noted previously, the process is carried out within a substantially air-tight enclosure to prevent outside air from entering the heat zone 31 of the retort between the heating rods 18 and the bed 13 of coal thereby creating an atmosphere that is substantially oxygen free. The belt 14 carries the coal from a position A to position B as shown in FIGURE 2. A top piece of coal 32 absorbs heat from the heating source before a lower piece of 'coal 33. The lower pieces of coal on the belt remain at substantially the temperature they had upon entering the retort, this temperature being substantially the temperature of the coal stored in the bin 10. The upper pieces of coal at position A rapidly increase in temperature from the original temperature. For example, with a heat source temperature of 1440 degrees Fahrenheit, the piece of coal 32 at position A absorbs suii'icient heat from the heat source and its temperature increases to slightly below the 1440 degrees Fahrenheit temperature of the heat source. A piece of coal at position C located at the bottom of the bed next to the belt 14 remains near the temperature at which it entered the retort.

As the temperature of the rst piece of coal 32 increases, it begins to release its constituents or volatile matter in the form of vapor. The vaporized constituents rapidly move away from the point of origin and percolate down through the coal bed, and are cooled and thereby condensed by the underlying unheated coal. As the coal travels through the retort the heat penetrates downwardly. The result is that the temperature of the piece of coal 33 when it reaches position D increases to the same temperature as the top piece of coal 32 when it was at position A. This second piece of coal 33 then releases its constituents in vapor form in a similar manner. The condensed constituents subsequently gravitate to a recovery zone 34. As the bed moves through the retort, the heat penetrates downwardly essentially creating a heat wedge from position A to position E. The ternperature of the bed above the imaginary line between position A and position E is relatively hot and the portion of the bed below this line is relatively cool, but it will be appreciated that the temperature varies through the bed rather than being markedly different on each side of the imaginary line. Thus, the heat progressively moves down through the bed as the bed moves with upper particles reaching a temperature to release constituents, while lower particles remain sufficiently cool to condense release vapors.

Hence, it will be apparent that as the coal progresses through the retort, successive pieces of coal are heated and release their volatile constituents which, in turn, are condensed upon passing by the unheated coal below. The condensed vapors are drawn off as liquid at the bottom, and it has been found that the liquid has substantially the same composition along the entire length of the retort. The constituents released including oil, water and gas gravitate to the recovery zone 34 by passing through the perforations in the belt 14.

The temperature in the heat zone 31 is sufficiently high so that the products are released rapidly in a gaseous state, the temperature being maintained above the temperature at which the chemicals in the recovered oil vaporize. The vapor passes downwardly from the point of origin and condenses by passing through the cooler material positioned below the point of release of the volatile matter. The vapors are thus efliciently condensed by the lower layer of cool coal along the entire bed. Processing piping for condensing the vapors is not required, and thus the cost thereof as well as the clogging thereof are eliminated. Since the products are released and withdrawn rapidly, most of the apparatus may be constructed of mild steel.

The pressure in the bed, and thus at the `point of release of the volatile matter, preferably is slightly below atmospheric pressure. As will be described subsequently, released gases are passed through a zero governor positioned outside the retort and coupled with the heat zone to maintain the appropriate pressure within the retort. The heat zone is maintained at approximately atmospheric pressure and the bed slightly below, there being a pressure differential across the bed.

The condensed products ow down a sloping plate beneath the belt 14, the products being withdrawn from the retort by gravity through goosenecks, or traps, to a sloping pipe. Gas is withdrawn and passed through a cyclone separator, or cyclonic action centrifuge, to separate any oil particles from the released gas.

Although not intending to be limited thereby an exemplary apparatus, which will be described subsequently, for carrying out the invention typically may be approximately 44 feet long and 6 feet wide. The belt 14 is stainless steel and travels the length of the apparatus or retort and may be driven by a ten horsepower motor. Coal is positioned on the belt in a bed which is approximately forty feet long, and typically three to four inches thick. The apparatus is completely sealed by water jackets and air-tight feeders. The heating rods are positioned along the entire length of the apparatus approximately one to two inches above the top of the bed. The apparatus may be readily expanded to process greater volumes of materials, such as by doubling the length and width of the belt and heating units and doubling the speed of the belt.

The coal travels the length of the retort with each piece remaining in the same relative position within the bed. The relative positions of the pieces of coal within the bed of coal must be maintained to ensure that cooler layers of material are beneath the material being heated and, accordingly, agitation of the coal as by belt vibration is to be avoided. Insulation, and/or reflectors above the heat source ensure that heat is directed downward toward the moving bed of coal.

Referring now to FIGURES 3 through 5, apparatus is illustrated for removing products from a moving bed of material particles according to the invention. FIGURE 3 essentially is a partial perspective view of the apparatus cross-sectioned along a line 3 3 of FIGURE 4. The apparatus includes a horizontal retort generally designated by a reference numeral 50 having water-jacketed side walls 51 and 52 and bottom wall 53. The bottom wall 53 is inclined under the belt 14, and the upper surface 54, which may be made of stainless steel, serves as adrain plate for condensed products.

The belt 14 is porous perforated and preferably is made of stainless steel having a mesh large enough for the condensed liquid to pass through but not the coal. The belt has a typical mesh of one-sixteenth of an inch, and is tempered to withstand the temperature at the exit end of the belt which is generally below one-thousand degrees. 'Ihe edges of the belt are supported by longitudinal platens 55 and 56 aixed to respective side walls 51 and 52, it being understood that bearings also may be provided if desired. The platens enable the belt 14 to move freely without vibrating the bed 13 of material. The belt 14 is mounted on drums 15 and 16 (not shown in FIGURE 3) at the ends of the retort as described in connection with FIGURE 1, the drum 16 being driven through suitable driving means 57, by a motor or the like, such as a ten horsepower-electric motor. The lower portion of the belt also may be supported by platens 58 and 59, if desired. A support plate 60 is aixed to the side wall 51, and the lower inclined Wall 53 may extend down at 61 for supporting the lower platens 58 and 59. A plurality of legs 62 and 63 are provided on each side of the retort for supporting the same.

Channel members 66 and 67 having a S-shaped crosssection are axed, as by welding, along the entire length of the top of the respective side walls 51 and 52 for supporting the top, generally designated by a numeral 70, of the retort and for providing a water seal. A pair of channel members 68 and 69` having a U-shaped crosssection are provided for holding a plurality of radiantheating rods 18, which may be electrical-heating rods, along the retort above the bed 13. Insulation 71, such as a ten-inch thick wet asbestos blanket, is arranged above the heating rods 18 and supported by the channel members 68 and 69. Preferably, a steel reflector (not shown) may be secured to the channel members 68 and 69 between the rods 18 and the insulation 71 to aid in refleeting heat downwardly toward the bed 13. A steel hood 72 is supported on top of the insulation 71 by the channel members 66 and 67. The steel hood includes a steel plate 73 and brace members 74, and may be removed to gain an access to the insulation or heating rods, or for removing the latter.

The inner portions 75 and 76 of the respective channel members 66 and 67 are closed at their ends and substantially lled with water. The outer downwardly turned portions 77 and 78 of the respective channel members 68 and 69 extend downwardly into the water in the respective portions 75 and 76 to provide a water seal at the top of the retort. Adjusting means in the form of screws 80, 81 and the nuts 82, 83 may be mounted on 'the braces 74 at the respective sides of the retort to enable appropriate positioning of the top 70 of the retort to ensure a proper water seal.

A plurality of liquid and gas take-offs 86 are coupled over openings 87 in the side wall 52. These take-offs include housings 87 having bottom wall 53 for receiving the condensed liquid products, and ducts 89 coupled over openings in the upper lportion of the respective housings and interconnected lby conduits 90 to allow the escape of gases. Each of the housings 86 includes an opening 92 at the bottom thereof communicating with a coupling 93 which in turn is connected to a gooseneck seal or trap 94, to ensure a proper air-tight seal for the retort. The traps are coupled with the downwardly sloping pipe 21 by means of couplings 96 which may be made of rubber 6 tubing. A lower end of the pipe 21 is connected with the storage tank 22 shown in FIGURE 1.

The end 98 of the duct 89 (note FIGURE 4) at the exit end of the retort is closed, a-nd the duct 89 at the entry end-of the retort is coupled through a conduit 99 to a Cyclonic-centrifugal separator 100 which separates oil particles, or mist, from the gas and tends to suck the gas from the retort. The separated oil may be withdrawn by means of a pipe 101 which in turn may be coupled with the pipe 21 if desired. The ga-s is then passed through a zerogovernor 102 to an outlet tube 103 for storage. The governor 102 may be a model 7218 atmospheric regulator made by North American Mfg. Co. A small amount of the gas may be fed from th-e governor 102 through a pipe 104 having outlets 105 back into the heating chamber or zone 31. The Zero governor 102 includes a large adjustable diaphragm which can be set to maintain the pressure within the heating chamber near atmospheric pressure by the return of a small amount of the gas through the pipe 104 and outlets 105 to the heating chamber. Without the governor 102, the centrifugal separator 100 tends t0 create a vacuum within the heating chamber above the bed 13 and this vacuum tends to allow oxygen to enter the chamber through any small holes or leaks that may exist in the retort. Oxygen entering the heating chamber will allow volatile matter to oxidize. Additionally, the Zero governor 102 prevents a high pressure from occurring in the heating chamber which tends to cause the expulsion of gases through any small holes that may exist in the retort. Thus, the zero governor serves to maintain the pressure in the heating chamber near atmospheric pressure and thus the pressure in the bed and beneath slightly below atmospheric pressure.

The gas returned to the heating chamber through the pipe 104 is returned just below the heating rods 18. This gas does not have any signicant volatile matter and forms a gas shield or layer underneath the heating rods preventing released gases from the bed 13 from penetra-ting the gas shield and reaching the heating rods. The released gases and volatile vapors and droplets are thus prevented from caking on the heating rods 18 causing breakage thereof. With the zero governor 102, the gas ows to the centrifugal separator 100 without any substantial amount of suction being provided. lf gas heaters are used rather than the electrical-heating rods 18, gas may be fed thereto for heating the bed 13.

The material, such as coal to be processed is fed onto the entry end of the belt 14 as illustrated in FIGURE 1 in a bed 13 having a thickness from two to six inches, typically three to four inches. The heat Zone temperature generally is maintained between approximately 1000` to 1440 degrees Fahrenheit. The bed of material moves through the retort as explained previously, with the released products being condensed by the cooler lower layer of the material. The volatile matter is released and condensed quickly maintaining cracking thereof to a minimum. The condensed products ow through the perforations in the belt 14, down the surface 54 and into the housings 87 with the gas or gases flowing into the ducts 89 as indicated by arrows 108. The liquid products ow through the traps 94 and the pipe 21 to the storage tank 22. The ga-s passes through the ducts 89 and conduits to the centrifugal separator 100. Any liquids separated by the separator may be withdrawn through the outlet pipe 101 and gas is fed to the zero governor 102. The gas is withdrawn through the lpipe 103 and a small amount of the gas returned to the hea-ting chamber through the pipe 104 and outlets 105. The coke or char passes to the elevator 19` and additional volatiles may be stripped therefrom and separated lby a centrifugal separator, and fed to the storage tank 22.

Coal ranging in size from one-eight inch to two and one-half inches has been processed according to the invention, but larger size coal may be processed. Exemplary coal which has been processed had the following assay: 45

percent fixed carbon; 45 percent volatile combustible matter; 9 percent ash; and 0.80 percent sulfur. The coal after being processed resulted in coke having the same shape as the particles of coal prior to being processed, and having the following assay: 75.5 percent fixed carbon; 4.5 percent volatile combustible matter; 15.1 percent ash; and 0.80 percent sulfur.

An approximate yield, for example, of a ton of coal processed according to the invention has been thirtyseven gallons of tar or heavy oil, 1950 cubic feet of gas having a heating value of approximately 919 gross B.t.u. per cubic foot, three gallons of distillate recovered from the gas, and 50 percent Iby volume of coke. Yields in percent by weight of coal approximately have been sixtynine percent coke having a 12 percent volatile content, 15 percent tar or heavy oil, 1 percent light oil, 10 percent water and percent gas.

In exemplary apparatus constructed according to the invention, coal travels through the retort in approximately three to twenty minutes in beds having a thickness of several inches. The heating source with electrical-heating rods 1S has a typical temperature of approximately 1440 degrees Fahrenheit, and the temperature may be higher with gas units. Either the source temperature, thickness of the bed or speed of the belt, or all of these, may be varied depending on the type of material being processed and the desired end products. At higher temperatures, a faster speed for the belt and/ or a thicker bed of material is used. For example, high temperatures and a long travel time cause the release of more volatile matter providing coke with a low volatile content which is preferred by certain industries, such as the phosphate industry.

The present embodiments of the invention are to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by -the foregoing description, and all changes which come within the meaning and range of equivalency of the claims therefore are intended to be embraced therein.

What is claimed is:

1. A process for removing constituents from material particles comprising the steps of forming said particles into an elongated and substantially horizontal bed having a thickness equivalent to at least several particles,

maintaining a slightly lower pressure near the bottom of said bed than near the top thereof,

enclosing said bed within a substantially oxygen free atmosphere, applying heat from a radiant heat source to the top of said bed substantially along the entire length thereof to volatilize constituents of said material,

feeding suicient cool material particles past said heat source to ensure a substantially cooler layer of particles beneath the layer of particles being heated to allow vaporized constituents to be condensed by contact with said cooler material particles thereby enabling gravity recovery of said vaporized constituents in liquid form, and

collecting said constituents.

2. A process as in claim 1 wherein the pressure at the top of said bed is maintained near atmospheric pressure.

3. A process as in claim 1 wherein the pressure at the bottom of said bed is slightly below atmospheric pressure, and

said vaporized constituents are allowed to exist from said enclosure and are collected.

4. A process as in claim 1 wherein the vaporized constituents include gas and vaporized liquid, the vaporized liquid being condensed by said relatively cooler lower particles and allowed to flow to a container, and said gas is allowed to exit from said enclosure and is collected.

5. A process as in claim 4 wherein said material is coal,

the temperature of said layer of particles being heated is in the approximate range of 1000 to l400 degrees Fahrenheit, and the pressure below said bed is slightly below atmospheric pressure, and said vaporized liquid includes oil which is condensed by said cooler particles. 6. Apparatus for the release and collection of constituents from material particles comprising an elongated and substantially air-tight enclosure, an elongated perforated belt mounted for movement in a substantially horizontal direction within said enclosure, radiant heating means mounted within said enclosure for directing heat downwardly toward said belt, feed means for supplying said material particles onto said belt in a bed whereby the top of said bed is heated by said heating means, said feed means feeding sufficient material particles onto said belt to insure a relatively cooler layer of material beneath an upper layer thereof being heated to enable vaporized constituents to be condensed by contact with said cooler layer of particles substantially along the entire length of said belt, collecting means communicating with the bottom of said bed through said belt for collecting liquid condensed through said cooler layer of said particles, said collecting means including drain means for receiving said liquid, and duct means mounted at a side of said enclosure above the level of liquid at said drain means for receiving gases released by said particles and means for effecting a slightly lower pressure in the bottom of the bed as compared with the top thereof. 7. Apparatus as in claim 6 wherein pressure equalizing means are coupled with said duct means and said enclosure to maintain the pressure within said enclosure in the vicinity of said bed near atmospheric pressure.

8. Apparatus as in claim 6 wherein said enclosure includes insulated side and end walls and an insulated top which is removably coupled with said side walls, and sealing means coupled between said top and said side walls for providing a substantially air-tight seal at the top of said enclosure. 9. Apparatus as in claim 8 wherein said heating means provides a temperature in excess of one thousand degrees.

10. Apparatus for the release and collection of constituents from material particles comprising a substantially air-tight enclosure, a perforated belt mounted for movement within said enclosure, means coupled with said enclosure for supplying said particles onto said belt in a bed having a substantial thickness, radiant heating means mounted above said bed for directing heat toward substantially the entire top of said bed for heating an upper layer of particles thereof and causing the release of constituents therefrom in the form of vapors, collecting means communicating with substantially the entire bottom of said bed through said belt for collecting liquids resulting from condensation of said vapors through a cooler lower layer of particles in said bed substantially along the entire length thereof and for collecting released gases, said collecting means including housing means having an opening therein communicating through air-seal means with a container, and including duct means communicating with separating means to allow gas to exit from said enclosure, and pressure regulating means connected with said separating means and said enclosure for supplying an amount of said gas into said enclosure above said bed to maintain the pressure within said enclosure above said bed near atmospheric pressure and for effecting collecting means coupled with one side of said enclosure for receiving said liquid constituents and for receiving released gases from said material particles, said c01- lecting means including tube means connected with said enclosure adjacent said pan for allowing the gravity withdrawal of said liquids, and including duct means coupled with said one side of said enclosure -above the level of liquid at said tube means for allowing the withdrawal of said released gases, and

ing gas from said enclosure, and

said pressure regulating means includes a pressure regulator coupled from said separator to a plurality of places along a side of said enclosure for supplying said amount of gas into said enclosure between said heating means and said bed.

12. Apparatus for the release and collection of constituents from material particles comprising a substantially air-tight enclosure having side walls and having a pan for receiving liquid constituents from said material particles, said enclosure having a top which is removably coupled with said side walls and having sealing means coupled between said top and said side walls for providing a substantially air-tight seal at the top of said enclosure,

a perforated belt mounted for movement within said enclosure and encircling said pan thereby forming top and bottom belt portions,

means adjacent said enclosure for supplying said particles onto said top portion of said belt in a bed having a thickness of several inches,

10 pressure regulating means connected with said duct means and said enclosure for supplying an amount of said released gases into said enclosure to maintain approximately atmospheric pressure within said enclosure near the top of said bed and a slightly lower pressure at the bottom of said bed and for maintaining a substantially oxygen free atmosphere within said enclosure, said pressure regulating means including a separator coupled to said duct means and a pressure regulator coupled between said separator and said enclosure.

13. Apparatus as in claim 12 wherein said pressure regulator has an output coupled with said enclosure between said heating means and said bed to provide a gas shield below said heating means to prevent Said vapors from impinging upon said heating means.

References Cited UNITED STATES PATENTS radiant heating means mounted within said enclosure 1,814,463 7/ 1931 Trent 202-117 above said bed for directing heat toward substantially 1,978,945 10/ 1934 Hereng 202-117 the entire top of said bed for heating an upper layer 2,533,492 12/ 195() Mekler 202-117 of particles thereof and causing the release of con- 3,226,212 12/ 1965 Ban 202-117 stituents therefrom in the form of vapors, the speed 3,325,395 6/1967 Ban 20i1 32 XR of said belt, the heat of said heating means and the rate of feed of said means supplying said particles maintaining sufficient particles in said bed to ensure a substantially cooler layer of said particles beneath the top of said bed being heated to allow vaporized constituents to be condensed by contact with said cooler particles thereby causing liquid constituents to llow to said pan,

NORMAN YUDKOFF, Primary Examiner D. EDWARDS, Assistant Examiner U.S. C1. XR. 

